1. Field of the Invention
The present invention relates to air pollution control equipment and more particularly, to a wetted wall venturi scrubber with a 2-stage venturi throat, which avoids clogging in the throat by dust particles.
2. Description of the Related Art
Venturi scrubbers have been extensively used in the removal of particles in the waste gas. A traditional venturi scrubber generally comprises a converging section, a diverging section and a throat. The throat is connected between the converging section and the diverging section. Waste gas and scrubbing fluid droplets are introduced into the converging section, and then accelerated in the throat section. The scrubbing fluid droplets collide with the particles due to the velocity difference between the particles and the droplets, thereby causing the particles to collide with the droplets by inertial impaction and are removed from the waste gas.
However, when waste gas of high particle concentration is introduced into the venturi scrubber, the particles tend to be adhered to the inner surface of the converging section and the throat. Accumulation of particles results in particle clogging in the scrubber, thereby causing operation instability and abnormal increase in the pressure drop of the air flow through the scrubber. Further, the traditional venturi scrubber has a special shape comprising converging section, throat and diverging section, which complicates the fabrication process.
In the paper by Tsai et al. (J. Air & Waste Manage. Assoc., 55: 319-235, 2005) and Huang et al. (J. Environ. Eng. ASCE, 133(4): 454-461, 2007), the particle collection efficiency of a traditional venturi scrubber was enhanced by condensational growth of fine particles before the scrubber. But the method to avoid particle clogging in the throat areas had never been mentioned. Both U.S. Pat. Nos. 5,336,284 and 4,043,772 disclose a venturi scrubber with an area-adjustable throat section. The users can change the throat cross sectional area according to the operating conditions. To avoid particle clogging, the throat cross sectional area can be increased while high-concentration aerosol particles are treated by the scrubber. But it will lead to the reduction of collection efficiency.